KLM KT34XA or Cushcraft X7/X9
jl...@uol.com.br
Tks in advance...
73 Lopes - PY2SM
mailto:jl...@uol.com.br
ICQ: 1477570
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William B Clark
Lopes,
By far, you can't go wrong with the KT34XA, I've built 9 of
them and have a new antenna in the box ready to build, for a new
installation. Quality is the key point. One I built in So. Cal, in
1981, is still up and working fine. What more can I say?
73, Bill
KD6UN
Lawrence Stoskopf
insulators...and was very impressed with the performance on a city lot
at about 40 feet. Directivity was as reasonable a can be expected with
it that low and the big advantage was that the SWR seemed as flat across
the band as specified. Of course, with the short boom length on the
four element version, it is basically a 3 element beam with a log feed.
After being in use for about two years, I was operating 15 M and
noted that the SWR was all wrong. A call to the designer, Mike Staal,
now of M2, brought a quick comment that water had gotten in the trap.
Seems that he had tested the traps for leakage in several ways including
sinking one in the ocean for a while and they were intact. Mine failed
in the summer after a 100 degree (F) day and a sudden shower. The
change from hot to cold with the rain makes a vacuum that wicked some of
the rainwater into the trap and changed 'things'. Was advised to clean
that trap and drill a small hole in the center tubing to get rid of the
pressure difference. I did that and it worked for another year when the
same happened to 20M. That time I broke a plastic insulator. They
promptly sent a new set...whoops, were clear rather than black. Seems
that the plastic was already UV protected and they really didn't need
the carbon black to protect it. Problem, that changed the dielectric
constant and the old dimensions didn't work. I reworked it again and
used it for maybe 12 years until moving to the country and putting up
only VHF antennas. I liked the looks, the structural design, the
bandwidth, but the design is a bit dated so rather than adding the
extension and cleaning the whole thing again and reassembling it to the
exact precision required for good performance:
I ordered the Cushcraft X-7. Talk about another pile of parts. It
appears that in an attempt to keep it light and UPS shippable, they
carried tapering of elements to the extreme. The boom comes in 5
segments, but seems solid enough. The 20M reflector has 11 parts. The
entire element set has about 70 segments. After putting it all together
there seemed to be enough flop in the longer elements that I was worried
that the strong Kansas winds would let the elements move around so
bought some stainless steel self tapping screws and added a screw at
each joint.That stiffened the whole thing.
I do like the hardware for stiffness, but the (KLM like) log feed is
a bit ackward. Finally, when after 3 evenings I took the sections
outside to assemble realized that what they had apparently done is
design a traped front director, back off for the log feed for the three
bands and space the reflectors for the bands behind. Without modeling
the antenna, it looks like only the front half of the boom is used on
10M! If so, what a waste of boom. You can download the assembly sheet
from the Cushcraft WEB site and see what you think.
Performance: It's up there now with a quarter inch of ice on it. Looks
a little droopy. Works well, I used the metric dimensions and if I read
the review in the RSGB journal correctly, those might be a bit off. SWR
is 1.2 on 10 and 20 and 1.5 minimum on 15. When the bands are open who
knows what the performance is. In the last CW DX contest contest was
working JAs off the front and South America off the back on 15. Of
course, in the previous SSB contest worked a lot of countries on 15
using an inverted V hung off the side of a nearby hill.
http://www.tri.net/~stoskopf/
I probably wouldn't buy another. Have a new KT-34 in the box in the
basement that I bought before I thought better of it. (It is a neat
portable FD type antenna as you can just pull the end elements out after
loosening the hose clamps, put the whole center assembly and ends in the
pickup and drive away.) The Force 12 looks like a lot of tubing in the
air.
Wish M2 would build a tri-bander. I have their 10 and 15 meter 4
element versions and can't say enough about ease of assembly, strength
and performance when I haul one up to the hilltop for portable
operation. Including survivability after I dropped the 15M vesion while
moving it from one side of the hill to the other. It bounced, in
another incident the Cushcraft equivalent gently bent.
Hope this helps
N0UU
Anthony R. Gold
stos...@tri.net "Lawrence Stoskopf" wrote:
> The Force 12 looks like a lot of tubing in the air.
Is that good or bad? All these antennas are a lot of tubing in the
air. Why does the Force 12 look more so, and what does that imply?
Regards,
--
Tony - G3SKR / W2TG email: tg...@panix.com